THE NERVOUS SYSTEM •!&;> It can be traced down to the lower part of the latter muscle into which it sinks. It also supplit- the sternc-and cleido-mastoid muscles. At the top of the neck it communicates with the vagus and cervical plex-i*. b"t not with the sympathetic cord. It is essentially similar in all the Apes. Hypoglossal Nerve.—The origin, course and relations are as in Man; and it likewise communicates vrith the vagus, sympathetic and lingual nerves. It sends the descendens hypoglossi to unite with the cervical nerves to form the ansa kypogio&s:. It also supplies the thyro-hyoid, genio-hyoid, genio-glossus and stylo-g:cs~*:i muscles. It is essentially similar in ail the Apes and Man. Section C.—THE SPINAL NERVES. THE CERVICAL PLEXTS. In all the Apes the first four cervical nerves unite in a looped manner to form the cervical plexus, whose position and relations are as in Man. There are slight differences in the branches ; and the latter form cutaneous, muscular and communicating groups. The fourth cervical nerve communicates with the fifth. The following table shows the branches in the Chimpanzee (fig. 54) :— A. Communicating Nerves (deep). (1) To vagus (G.N.), accessory (XI), hypo-glossal (XII), from Cl and C2 and sympathetic. B. Muscular Branches (deep). Sterno-inastoid (S-M.) from C2. Trapezius (Tra.) from C3 and C4. Levator anguli scapulae (L.A.S.) from 03.